Semiconductor devices including a stressor in a recess and methods of forming the same

ABSTRACT

Semiconductor devices including a stressor in a recess and methods of forming the semiconductor devices are provided. The methods may include forming a fast etching region comprising phosphorous in an active region and forming a first trench in the active region by recessing the fast etching region. The methods may also include forming a second trench in the active region by enlarging the first trench using a directional etch process and forming a stressor in the second trench. The second trench may include a notched portion of the active region.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/033,639, filed Sep. 23, 2013 in the United States Patent andTrademark Office and claims the benefit of Korean Patent Application No.10-2012-0133248, filed on Nov. 22, 2012 in the Korean IntellectualProperty Office, the disclosures of which are incorporated by referenceherein in their entireties.

FIELD

The present disclosure generally relates to the field of electronics,and more particularly, to semiconductor devices.

BACKGROUND

To improve electrical characteristics of semiconductor devices, avariety of strain technologies have been developed.

SUMMARY

A method of forming a semiconductor device may include forming a lightlydoped drain (LDD) in an active region in a substrate and forming a fastetching region including phosphorous in the LDD. The method may alsoinclude forming a first trench in the active region by recessing thefast etching region and forming a second trench in the active region byenlarging the first trench using a directional etch process. The secondtrench may include a notched portion of the active region. The methodmay further include forming a stressor in the second trench and forminga gate electrode on the active region. In various embodiments, the LDDmay include boron.

According to various embodiments, forming the first trench may includeperforming an isotropic etch process. The first trench may include anupper trench formed by recessing the fast etching region and a lowertrench connected to a lower portion of the upper trench. The lowertrench may have a first width narrower than a second width of the uppertrench. In various embodiments, forming the first trench further mayinclude performing an anisotropic etch process before performing theisotropic etch process.

According to various embodiments, the notched portion of the activeregion may include an upper sidewall and a lower sidewall contacting theupper sidewall. An angle between an uppermost surface of the activeregion and the upper sidewall may be an acute angle and the uppersidewall may be non-coplanar with the lower sidewall. In variousembodiments, the upper sidewall may contact the lower sidewall at aconvergence interface on a surface of the LDD. The gate electrode mayoverlap the convergence interface of the upper and lower sidewalls andan edge portion of the upper sidewall may protrude beyond an adjacentsidewall of the gate electrode.

In various embodiments, a width of the fast etching region may benarrower than a width of the LDD. A first depth of the fast etchingregion may be shallower than a second depth of the LDD. A portion of theLDD may be formed between the active region and the fast etching region.A portion of the fast etching region may be between the LDD and thestressor, after forming the stressor.

According to various embodiments, the method may further include forminga preliminary gate electrode on the active region and a spacer on asidewall of the preliminary gate electrode before forming the LDD andremoving the preliminary gate electrode after forming the stressor.

According to various embodiments, the method may further include forminga preliminary gate electrode on the active region and a spacer on asidewall of the preliminary gate electrode before forming the fastetching region and removing the preliminary gate electrode after formingthe stressor.

In various embodiments, the method may further include forming apreliminary gate electrode on the active region and a spacer on asidewall of the preliminary gate electrode before forming the firsttrench and removing the preliminary gate electrode after forming thestressor.

According to various embodiments, forming the stressor may includeforming a first semiconductor layer in the second trench, forming asecond semiconductor layer on the first semiconductor layer and forminga third semiconductor layer on the second semiconductor layer. The firstand second semiconductor layers may include a material absent from theactive region. Forming the first, second and third semiconductor layersmay include performing selective epitaxial growth (SEG) processes.According to various embodiments, the first and second semiconductorlayers may include respective silicon germanium layers, and a germaniumconcentration of the second semiconductor layer may be greater than thatof the first semiconductor layer. The third semiconductor layer mayinclude a Si layer.

A method of forming a semiconductor device may include forming a firstlightly doped drain (LDD) in a first active region and a second LDD in asecond active region and forming a first fast etching region in thefirst LDD of the first active region and a second fast etching region inthe second LDD of the second active region. The first active region maybe in a first region of a substrate and the second active region may bein a second region of the substrate. The first and second fast etchingregions may include phosphorous. The method may also include forming afirst preliminary trench and a second preliminary trench by recessingthe first and second fast etching regions, respectively, and forming afirst trench and a second trench by enlarging the first and secondpreliminary trenches, respectively, using a directional etch process.The first trench may include a first notched portion of the first activeregion and the second trench may include a second notched portion of thesecond active region. The method may further include forming a firststressor in the first trench and a second stressor in the second trenchand forming a first gate electrode on the first active region and asecond gate electrode on the second active region.

According to various embodiments, the first notched portion of the firstactive region may include a first upper sidewall contacting a firstlower sidewall at a first convergence interface and the second notchedportion of the second active region may include a second upper sidewallcontacting a second lower sidewall at a second convergence interface.The first gate electrode may overlap the first convergence interface andthe second gate electrode may not overlap the second convergenceinterface. The first convergence interface may be higher than the secondconvergence interface.

In various embodiments, a horizontal distance between the firstconvergence interface and a sidewall of the first gate electrode may bein a range of 0 nm to 5 nm, and a horizontal distance between the secondconvergence interface and a sidewall of the second gate electrode may bein a range of 1 nm to 3 nm.

In various embodiments, a vertical distance between the firstconvergence interface and an uppermost surface of the first activeregion may be in a range of 3 nm to 7 nm and a vertical distance betweenthe second convergence interface and an uppermost surface of the secondactive region may be in a range of 8 nm to 12 nm.

According to various embodiments, the first convergence interface may beformed on a surface of the first LDD, and the second convergenceinterface may be formed on a surface of the second LDD and wherein aboron concentration of the second LDD may be greater than a boronconcentration of the first LDD.

In various embodiments, a phosphorous concentration of the second fastetching region may be less than a phosphorous concentration of the firstfast etching region.

A semiconductor device may include a substrate including first andsecond regions, a first gate electrode on a first active region in thefirst region, a first trench in the first active region adjacent a sideof the first gate electrode and a first embedded stressor in the firsttrench. The device may also include a second gate electrode on a secondactive region in the second region, a second trench in the second activeregion adjacent a side of the second gate electrode and a secondembedded stressor in the second trench. The first and second regions mayinclude different respective pattern densities. The first active regionmay include a first notched portion of the first active region and thesecond trench may include a second notched portion of the second activeregion. The first notched portion may include a first upper sidewall anda first lower sidewall contacting the first upper sidewall, and thefirst upper sidewall and the first lower sidewall may converge at afirst convergence interface. The second notched portion may include asecond upper sidewall and a second lower sidewall contacting the secondupper sidewall, and the second upper sidewall and the second lowersidewall may converge at a second convergence interface. The first gateelectrode may overlap the first convergence interface and the secondgate electrode may not overlap the second convergence interface and thefirst convergence interface may be higher than the second convergenceinterface.

A semiconductor device may include a substrate including an activeregion, a gate electrode on the active region and a lightly doped drain(LDD) in the active region adjacent a side of the gate electrode, theLDD including boron and phosphorous. A concentration of the phosphorousmay be in a range of 5E18 atoms/cm3 to 1E19 atoms/cm3. The device mayalso include trench in the active region adjacent the side of the gateelectrode, the trench including a notched portion of the active regionand an embedded stressor in the trench.

A method of forming a semiconductor device may include forming a gatestructure on a substrate and forming a doped pattern adjacent a side ofthe gate structure in the substrate. The method may also include forminga first preliminary cavity by etching a portion of the doped patternusing the gate structure as an etch mask, forming a second preliminarycavity by selectively etching the doped pattern, forming a cavity byetching exposed surfaces of the second preliminary cavity using adirectional etch process and forming a stressor in the cavity. A side ofthe first preliminary cavity may expose the doped pattern. The cavitymay include a recess under the gate structure and the recess may includetwo converging sloped portions.

In various embodiments, forming the doped pattern may include implantingelements into the substrate using the gate structure as an implant mask.Implanting the elements may include implanting phosphorous into thesubstrate

According to various embodiments, the method may further include forminga lightly doped drain (LDD) in the substrate adjacent the side of thegate structure before forming the doped pattern. At least a portion ofthe doped pattern may be formed in the LDD. The method may additionallyinclude forming a spacer pattern on a side of the gate structure afterforming the LDD. Implanting the elements may include implanting theelements using the spacer pattern and the gate structure as an implantmask

In various embodiments, the directional etch process may include an etchprocess etching the substrate at a plurality of different etch ratesaccording to crystal orientations of the substrate and the recess mayinclude a notched portion including the two conversing sloped portions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a method of forming a semiconductordevice according to some embodiments of the present inventive concepts.

FIGS. 2, 3, 4A, 4B, 5A-5C, 6A-6C, 7A-7C, 8A-8C, 9-13 and 14A-14G arecross-sectional views illustrating intermediate structures provided inoperations of forming a semiconductor device according to someembodiments of the present inventive concepts.

FIG. 15 is a cross-sectional view illustrating an intermediate structureprovided in operations of forming a semiconductor device according tosome embodiments of the present inventive concepts.

FIG. 16 is a layout of a semiconductor device according to someembodiments of the present inventive concepts.

FIGS. 17-24, 25A-25C, 26-30, and 31A-31C are cross-sectional views takenalong lines I-I′ and II-II′ of FIG. 16 illustrating intermediatestructures provided in operations of forming a semiconductor deviceaccording to some embodiments of the present inventive concepts.

FIG. 32 is a layout of a semiconductor device according to someembodiments of the present inventive concepts.

FIGS. 33-38 are cross-sectional views illustrating intermediatestructures provided in operations of forming a semiconductor deviceaccording to some embodiments of the present inventive concepts.

FIGS. 39 and 40 are a perspective view and a block diagram of anelectronic apparatus, respectively, according to some embodiments of thepresent inventive concepts.

FIG. 41 is a block diagram of an electronic system according to someembodiments of the present inventive concepts.

DETAILED DESCRIPTION

Example embodiments are described below with reference to theaccompanying drawings. Many different forms and embodiments are possiblewithout deviating from the spirit and teachings of this disclosure andso the disclosure should not be construed as limited to the exampleembodiments set forth herein. Rather, these example embodiments areprovided so that this disclosure will be thorough and complete, and willconvey the scope of the disclosure to those skilled in the art. In thedrawings, the sizes and relative sizes of layers and regions may beexaggerated for clarity. Like reference numbers refer to like elementsthroughout.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements. Other words used to describe relationships betweenelements should be interpreted in a like fashion (i.e., “between” versus“directly between,” “adjacent” versus “directly adjacent,” etc.).

It will be understood that, although the terms first, second, etc. maybe used herein in reference to elements of the invention, such elementsshould not be construed as limited by these terms. For example, a firstelement could be termed a second element, and a second element could betermed a first element, without departing from the scope of the presentinvention. Herein, the term “and/or” includes any and all combinationsof one or more referents.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the figures. It will be understood thatthe spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The terminology used herein to describe embodiments of the invention isnot intended to limit the scope of the invention. The articles “a,”“an,” and “the” are singular in that they have a single referent,however the use of the singular form in the present document should notpreclude the presence of more than one referent. In other words,elements of the invention referred to in the singular may number one ormore, unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “comprises,” “comprising,” “includes,” and/or“including,” when used herein, specify the presence of stated features,items, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features, items,steps, operations, elements, components, and/or groups thereof.

Embodiments are described herein with reference to cross-sectionalillustrations that are schematic illustrations of idealized embodiments(and intermediate structures). As such, variations from the shapes ofthe illustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, embodiments should not beconstrued as limited to the particular shapes of regions illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the figures are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to limit the scope ofthe present inventive concepts.

Unless otherwise defined, all terms (including technical and scientificterms) used herein are to be interpreted as is customary in the art towhich this invention belongs. It will be further understood that termsin common usage should also be interpreted as is customary in therelevant art and not in an idealized or overly formal sense unlessexpressly so defined herein.

It should also be noted that in some alternate implementations, thefunctions/acts noted in flowchart blocks herein may occur out of theorder noted in the flowcharts. For example, two blocks shown insuccession may in fact be executed substantially concurrently or theblocks may sometimes be executed in the reverse order, depending uponthe functionality/acts involved. Moreover, the functionality of a givenblock of the flowcharts and/or block diagrams may be separated intomultiple blocks and/or the functionality of two or more blocks of theflowcharts and/or block diagrams may be at least partially integrated.Finally, other blocks may be added or inserted between the blocks thatare illustrated, and/or blocks/operations may be omitted withoutdeparting from the scope of the present inventive concepts.

Although a transistor including a stressor in a recess may improvecarrier mobility, there may be large variations in sizes and shapes ofrecesses within a device. Various embodiments of the present inventiveconcepts, however, provide methods of forming a semiconductor device,the methods including forming a faster etch rate part which may enablecontrol of a size and a shape of a recess. Accordingly, the methodsdescribed herein may reduce variations in sizes and shapes of recesseswithin a device.

FIG. 1 is a flowchart illustrating a method of forming a semiconductordevice according to some embodiments of the present inventive concepts.FIGS. 2, 3, 4A, 4B, 5A-5C, 6A-6C, 7A-7C, 8A-8C, 9-13 and 14A-14G arecross-sectional views illustrating intermediate structures provided inoperations of forming a semiconductor device according to someembodiments of the present inventive concepts.

Referring to FIG. 1, a method of forming a semiconductor deviceaccording to some embodiments of the present inventive concepts mayinclude forming a lightly doped drain (LDD) (Block 500), forming afaster etch rate part (Block 510), forming a first trench (Block 520),forming a second trench (Block 530), forming a first semiconductor layer(Block 540), forming a second semiconductor layer (Block 550), forming athird semiconductor layer (Block 560), and forming an interlayerinsulating layer (Block 570).

Referring to FIGS. 1 and 2, a well 22, an active region 23, a deviceisolation layer 29, a buffer layer 31, a temporary gate electrode 33, afirst mask pattern 35, and a second mask pattern 37 may be formed on asubstrate 21. The substrate 21 may be a single-crystalline semiconductorsubstrate such as a silicon wafer or a silicon on insulator (SOI) wafer.The substrate 21 may include first conductivity-type impurities. Thewell 22 may include second conductivity-type impurities different fromthe first conductivity-type impurities.

Hereinafter, the description will be made under the assumption that thefirst conductivity-type is p-type and the second conductivity-type isn-type. In some embodiments, however, the first conductivity-type may ben-type and the second conductivity type may be p-type. For example, thesubstrate 21 may be single crystalline silicon including p-typeimpurities, and the well 22 is single crystalline silicon includingn-type impurities. The substrate 21 may include boron (B), and the well22 may include As, P, or a combination thereof.

The active region 23 may be confined to the well 22 by the deviceisolation layer 29. The active region 23 may include single crystallinesilicon including n-type impurities. The device isolation layer 29 maybe formed using a shallow trench isolation (STI) technique. The deviceisolation layer 29 may include an insulating layer such as siliconoxide, silicon nitride, silicon oxy-nitride, or a combination thereof.The buffer layer 31 may be interposed between the active region 23 andthe temporary gate electrode 33. The buffer layer 31 may include aninsulating layer such as silicon oxide, silicon nitride, siliconoxy-nitride, or a combination thereof. For example, the buffer layer 31may include silicon oxide.

The temporary gate electrode 33 may be formed to cross the active region23. The temporary gate electrode 33 may cross the active region 23 andthe device isolation layer 29. The temporary gate electrode 33 mayinclude polysilicon. In some embodiments, the temporary gate electrode33 may include an insulating layer. The first mask pattern 35 may beformed on the temporary gate electrode 33. The first mask pattern 35 mayinclude a material having an etch selectivity with respect to thetemporary gate electrode 33. The second mask pattern 37 may be formed onthe first mask pattern 35. The second mask pattern 37 may include amaterial having an etch selectivity with respect to the first maskpattern 35. For example, the first mask pattern 35 may include siliconoxide. The second mask pattern 37 may include silicon nitride orpolysilicon. In some embodiments, one of the first mask pattern 35 andthe second mask pattern 37 may be omitted.

Sides of the second mask pattern 37, first mask pattern 35, temporarygate electrode 33, and buffer layer 31 may be vertically aligned. Thesecond mask pattern 37, the first mask pattern 35, the temporary gateelectrode 33, and the buffer layer 31 may be referred to as a temporarygate pattern 31, 33, 35, and 37. The temporary gate pattern 31, 33, 35,and 37 may cross the active region 23. A plurality of the temporary gatepatterns 31, 33, 35, and 37 may be formed in parallel on the activeregion 23.

Referring to FIGS. 1 and 3, a first spacer 42 may be formed on asidewall of the temporary gate electrode 33. A lightly doped drain (LDD)43 may be formed by implanting the first conductivity-type impurities inthe active region 23 using the first spacer 42, the second mask pattern37, the first mask pattern 35, and the temporary gate electrode 33 as anion-implantation mask (Block 500). For example, the formation of the LDD43 may be done at a dose of 1E13 to 5E14 atoms/cm2 of BF₂ and anion-implantation energy of 2 to 5 Kev. The LDD 43 may include boron. Ahalo 45 may be formed by implanting the second conductivity-typeimpurities to the active region 23. The halo 45 may cover a side and abottom of the LDD 43. The formation of the LDD 43 and the halo 45 mayinclude an ion-implantation process and a heat treatment process.

The first spacer 42 may conformally cover an upper surface of thesubstrate 21. For example, the first spacer 42 may cover upper and sidesurfaces of the temporary gate pattern 31, 33, 35, and 37, and cover theactive region 23 and the device isolation layer 29 with a constantthickness. The first spacer 42 may include an insulating layer such assilicon oxide, silicon nitride, silicon oxy-nitride, or a combinationthereof. The first spacer 42 may include a material having an etchselectivity with respect to the temporary gate electrode 33. Forexample, the first spacer 42 may include silicon nitride. The LDD 43 maybe formed to reach a certain depth from an upper surface of the activeregion 23. The LDD 43 may partially overlap a bottom of the temporarygate pattern 31, 33, 35, and 37. The LDD 43 may be formed at a desiredposition by adjusting the thickness of the first spacer 42.

Referring to FIGS. 1 and 4A, a second spacer 47 may be formed on thefirst spacer 42. A faster etch rate part 49 may be formed in the activeregion 23 using the second spacer 47 as an ion-implantation mask (Block510). For example, the formation of the faster etch rate part 49 may bedone at a dose of 5E14 to 3E15 atoms/cm2 of PH₃ and an ion-implantationenergy of 2 to 5 Kev. PH₂ may be used instead of the PH₃. The fasteretch rate part 49 may include phosphorous (P).

The second spacer 47 may conformally cover the substrate 21. Forexample, the second spacer 47 may cover upper and side surfaces of thetemporary gate pattern 31, 33, 35, and 37, and cover the LDD 43 and thedevice isolation layer 29. The second spacer 47 may include aninsulating layer such as silicon oxide, silicon nitride, siliconoxy-nitride, or a combination thereof. The second spacer 47 may includea material having an etch selectivity with respect to the temporary gateelectrode 33. For example, the second spacer 47 may include siliconnitride. The first spacer 42 and the second spacer 47 may sequentiallycover the side surface of the temporary gate pattern 31, 33, 35, and 37.

The faster etch rate part 49 may be formed at a desired position byadjusting the thickness of the second spacer 47. The faster etch ratepart 49 may be formed in the LDD 43. A bottom of the faster etch ratepart 49 may be formed at a higher level than a bottom of the LDD 43. Thefaster etch rate part 49 may be formed to be aligned with an outer sideof the temporary gate electrode 33. The active region 23 may be retainedunder the temporary gate electrode 33. The LDD 43 may be retained underthe temporary gate electrode 33. The LDD 43 may be retained between thefaster etch rate part 49 and the active region 23.

Referring to FIGS. 1 and 4B, a second spacer 47A may be formed to havevarious thicknesses. For example, the second spacer 47A may be formed tohave a thickness of 1 to 3 nm. The second spacer 47A may function tocontrol the location of the faster etch rate part 49. For example, aside of the faster etch rate part 49 may be controlled to be located inthe LDD 43 by adjusting the thickness of the second spacer 47A. Thefaster etch rate part 49 may be controlled to be spaced apart from thetemporary gate electrode 33 by adjusting the thickness of the secondspacer 47A. The LDD 43 may be retained between the faster etch rate part49 and the active region 23.

In some embodiments, the faster etch rate part 49 may pass through theLDD 43. For example, the bottom of the faster etch rate part 49 may beformed in the halo 45. Further, the faster etch rate part 49 may passthrough both of the LDD 43 and the halo 45.

Referring to FIGS. 1 and 5A, a third spacer 51 may be formed on thesecond spacer 47. The formation of the third spacer 51 may include athin-film formation process and an anisotropic etching process. Duringthe formation of the third spacer 51, the second spacer 47 and the firstspacer 42 may be partially removed to expose an upper surface of thefaster etch rate part 49. The second spacer 47 and the first spacer 42may be retained between the temporary gate pattern 31, 33, 35, and 37and the third spacer 51.

The third spacer 51 may include an insulating material such as siliconoxide, silicon nitride, silicon oxy-nitride, or a combination thereof.The third spacer 51 may include a material having an etch selectivitywith respect to the temporary gate electrode 33. For example, the thirdspacer 51 may include silicon nitride.

Referring to FIGS. 1 and 5B, during the formation of the third spacer51, the faster etch rate part 49 may be partially removed to form arecess area 51T. For example, the recess area 51T may have a depth of 1nm to 10 nm.

Referring to FIGS. 1 and 5C, after the formation of the third spacer 51,a recess area 51T may be formed using an additional anisotropic etchingprocess. The recess area 51T may pass through the faster etch rate part49 and the LDD 43. For example, the recess area 51T may have a depth of7 nm to 10 nm. A bottom of the recess area 51T may expose the halo 45.Sidewalls of the recess area 51T may be vertically aligned with sidesurfaces of the third spacer 51.

Referring to FIGS. 1, 6A, and 6B, the faster etch rate part 49, the LDD43, and the halo 45 may be etched to form a first trench 53 (Block 520).The first trench 53 may include an upper trench 53A aligned with thefaster etch rate part 49 and a lower trench 53B connected to a bottom ofthe upper trench 53A. The upper trench 53A may be formed in the LDD 43.Due to the upper trench 53A, an under-cut may be formed under the firstspacer 42, the second spacer 47, and the third spacer 51. The lowertrench 53B may pass through the LDD 43 to be formed in the halo 45. Thelower trench 53B may have a width smaller than a width of the uppertrench 53A. A sidewall of the first trench 53 may have a step. Forexample, a side surface of the LDD 43, which is exposed by the uppertrench 53A and lower trench 53B, may have a step.

The formation of the first trench 53 may include a dry-etch process, awet-etch process, or a combination thereof. The formation of the firsttrench 53 may include an isotropic etch process, an anisotropic etchprocess, or a combination thereof. For example, the formation of thefirst trench 53 may include an isotropic dry-etch process using HBr,CF₄, O₂, Cl₂, NF₃, or a combination thereof. According to someembodiments, single crystalline silicon containing phosphorous (P),which has an etch rate higher than that of single crystalline siliconcontaining boron (B), may be included in the faster etch rate part 49,and thus the faster etch rate part 49 may have an etch rate higher thanthat of the LDD 43. Depending on the configuration of the faster etchrate part 49 and the LDD 43, the size and shape of the upper trench 53Aand lower trench 53B may be determined. The size, shape, and location ofthe first trench 53 may be controlled as desired, using theconfiguration of the faster etch rate part 49 and the LDD 43. The firsttrench 53 may be uniformly formed over the entire surface of thesubstrate 21.

Referring to FIG. 6C, in some embodiments, the faster etch rate part 49may be retained between the upper trench 53A and the LDD 43.

Referring to FIGS. 1 and 7A, a second trench 55 may be formed using adirectional etch process (Block 530). For example, the formation of thesecond trench 55 may include a wet-etch process using NH₄OH, NH₃OH, TMAH(Tetra Methyl Ammonium Hydroxide), KOH, NaOH, BTMH(benzyltrimethylammonium hydroxide), or a combination thereof. Theactive region 23 may have a sigma shape (Σ-shape) due to the secondtrench 55. The LDD 43 may be retained under the temporary gate pattern31, 33, 35, and 37. The active region 23 may include a first surface 23SU, a first side surface 23S1, a second side surface 23S2, and a secondsurface 23S3. A first edge E1 may be defined between the first sidesurface 23S1 and the first surface 23 SU. A second edge E2 may bedefined between the first side surface 23S1 and the second side surface23S2. Each of the first side surface 23S1 and the second side surface23S2 may include a {111} crystal plane. The second trench 55 may beinterpreted as an extension of the first trench 53.

Referring to FIG. 7B, the second trench 55 may pass through the LDD 43and the halo 45. The first surface 23SU may be defined on an upper endof the active region 23. For example, the first surface 23SU may be incontact with the buffer layer 31 and extend below the first spacer 42.The second trench 55 may expose the first side surface 23S1, the secondside surface 23S2, and the second surface 23S3. The first side surface23S1 may be connected to the first surface 23SU. The first side surface23S1 may form an acute angle with respect to the first surface 23SU. Thesecond side surface 23S2 may be formed under the first side surface23S1. The second side surface 23S2 may have a different angle from thefirst side surface 23S1. The second side surface 23S2 may form an acuteangle with respect to a horizontal extension line, which is parallel tothe substrate 21 and passes through the second surface 23S3. A bottom ofthe second trench 55 may expose the second surface 23S3. The secondsurface 23S3 may be connected to the second side surface 23S2. The firstsurface 23SU may be interpreted as an upper surface of the active region23.

The first edge E1 and the second edge E2 may be formed at a desiredposition by controlling the location of the faster etch rate part 49.For example, the first edge E1 may be formed under the first spacer 42,and the second edge E2 may be formed to overlap a bottom of thetemporary gate electrode 33. The first edge E1 and the second edge E2may be located on a surface of the LDD 43. The first side surface 23S1may expose the LDD 43. The second side surface 23S2 may expose the LDD43, the halo 45, and the active region 23.

A horizontal distance X may be defined between the second edge E2 and astraight line which is perpendicular to the substrate 21 and passesthrough a side surface of the temporary gate electrode 33. A verticalheight Y may be defined between the second edge E2 and a straight linewhich is parallel to the substrate 21 and passes through the firstsurface 23SU. For example, the horizontal distance X may be from 0 to −5nm, and the vertical height Y may be from 3 nm to 7 nm. When thehorizontal distance X is zero, it may be understood that the second edgeE2 is vertically overlapped by the side surface of the temporary gateelectrode 33, and when the horizontal distance X is a negative (−)value, it may be understood that the second edge E2 is verticallyoverlapped by the bottom of the temporary gate electrode 33. Inaddition, when the horizontal distance X is a positive (+) value, it maybe understood that the second edge E2 may be aligned with the outer sideof the temporary gate electrode 33.

The horizontal distance X and the vertical height Y may be uniformlycontrolled over the entire surface of the substrate 21 by adjusting thelocation of the faster etch rate part 49. In some embodiments, it ispossible to relatively decrease the vertical height Y while increasingthe absolute value of the horizontal distance X. A semiconductor deviceaccording to some embodiments of the present inventive concepts may havegood electrical characteristics according to the horizontal distance Xand the vertical height Y. According to some embodiments, asemiconductor device that includes the second edge E2 located on thesurface of the LDD 43 may show good electrical characteristics.

Referring to FIG. 7C, in some embodiments, the faster etch rate part 49may be retained between the second trench 55 and the LDD 43.

Referring to FIGS. 1 and 8A, a first semiconductor layer 61 may beformed in the second trench 55 (Block 540). The first semiconductorlayer 61 may include undoped single crystalline SiGe formed by aselective epitaxial growth (SEG) method. The Ge content in the firstsemiconductor layer 61 may be from 10 to 25%. The first semiconductorlayer 61 may conformally cover an inner wall of the second trench 55.The first semiconductor layer 61 may cover the first side surface 23S1and the second side surface 23S2 with a constant thickness.

Referring to FIG. 8B, a first semiconductor layer 61A may be formed tocover the second side surface 23S2 with a constant thickness and topartially expose the first side surface 23S1.

Referring to FIG. 8C, a first semiconductor layer 61B may be formed tocover the first side surface 23S1 and the second side surface 23S2.

Referring to FIGS. 1 and 9, a second semiconductor layer 62 may beformed in the second trench 55 (Block 550). The second semiconductorlayer 62 may include B-doped single crystalline SiGe by an SEG method.The Ge content in the second semiconductor layer 62 may be from 25 to50%. The second semiconductor layer 62 may contain 1E20 to 3E20atoms/cm3 of B. The second semiconductor layer 62 may fully fill thesecond trench 55. An upper end of the second semiconductor layer 62 maybe at higher level than the active region 23.

Referring to FIGS. 1 and 10, a third semiconductor layer 63 may beformed on the second semiconductor layer 62 (Block 560). The thirdsemiconductor layer 63 may include B-doped single crystalline silicon bythe SEG method. The third semiconductor layer 63 may contain 1E20 to3E20 atoms/cm3 of B. The first semiconductor layer 61, the secondsemiconductor layer 62, and the third semiconductor layer 63 may form anembedded stressor 65. The embedded stressor 65 may be referred to as astrain-inducing pattern. In some embodiments, the first semiconductorlayer 61 or the third semiconductor layer 63 may be omitted.

Referring to FIGS. 1 and 11, an interlayer insulating layer 71 may beformed on the substrate 21 (Block 570). The interlayer insulating layer71 may include an insulating layer such as silicon oxide, siliconnitride, silicon oxy-nitride, or a combination thereof. In someembodiments, several additional processes, such as a metal silicideformation process and a heat treatment process, may be performed on thethird semiconductor layer 63 before the formation of the interlayerinsulating layer 71.

Referring to FIGS. 1 and 12, the temporary gate electrode 33 may beexposed by partially removing the interlayer insulating layer 71 andremoving the second mask pattern 37 and the first mask pattern 35. Theremoval of the interlayer insulating layer 71, the second mask pattern37, and the first mask pattern 35 may be performed by a chemicalmechanical polishing (CMP) process, an etch-back process, or acombination thereof.

Referring to FIGS. 1 and 13, a gate trench 33T exposing the activeregion 23 may be formed by removing the temporary gate electrode 33 andthe buffer layer 31.

Referring to FIGS. 1 and 14A, a first gate dielectric layer 73, a secondgate dielectric layer 75, a first gate electrode 77, and a second gateelectrode 79 may be formed in the gate trench 33T.

The first gate dielectric layer 73 may be formed on the active region23. The first gate dielectric layer 73 may be referred to as aninterfacial oxide layer. The first gate dielectric layer 73 may beformed by a cleaning process. The first gate dielectric layer 73 mayinclude silicon oxide. The second gate dielectric layer 75 may includesilicon oxide, silicon nitride, silicon oxy-nitride, a high-K dielectricmaterial, or a combination thereof. For example, the second gatedielectric layer 75 may include HfO or HfSiO. The second gate dielectriclayer 75 may surround a side and a bottom of the first gate electrode77. The first gate dielectric layer 73 may be interposed between theactive region 23 and the second gate dielectric layer 75.

The first gate electrode 77 may surround a side and a bottom of thesecond gate electrode 79. The first gate electrode 77 may include aconductive material chosen by considering a work-function. For example,the first gate electrode 77 may include TiN or TaN. The second gateelectrode 79 may include a metal layer. In some embodiments, the firstgate electrode 77 may include TiAl or TiAlC.

Referring to FIG. 14B, the embedded stressor 65 may pass through the LDD43 and the halo 45 to be in contact with the active region 23. A bottomof the embedded stressor 65 may be formed at a lower level than the halo45. The embedded stressor 65 may be in contact with the first sidesurface 23S1 and the second side surface 23S2. The first semiconductorlayer 61 may be interposed between the LDD 43 and the secondsemiconductor layer 62.

The concentration of the first conductivity-type impurities in thesecond semiconductor layer 62 may be higher than that in the LDD 43. Forexample, a boron (B) concentration in the second semiconductor layer 62may be higher than that in the LDD 43. The first conductivity-typeimpurities in the second semiconductor layer 62 may diffuse into thefirst semiconductor layer 61. The boron (B) concentration in the firstsemiconductor layer 61 may be lower than that in second semiconductorlayer 62.

Phosphorous (P) implanted in the faster etch rate part 49 (e.g., asillustrated in FIG. 4A) may diffuse into the LDD 43. The LDD 43 maycontain phosphorous and boron. For example, the LDD 43 may contain 5E18to 1E19 atoms/cm3 of phosphorous. While implanting phosphorous to thefaster etch rate part 49, the phosphorous may remain in the secondspacer 47, the first spacer 42 and an interface thereof. The phosphorousmay remain in the third spacer 51 and an interface between the thirdspacer 51 and the second spacer 47. The phosphorous may remain in theembedded stressor 65 and interfaces between the embedded stressor 65 andthe first, second and third spacers 42, 47, 51. In some embodiments, thephosphorous may also remain in the LDD 43 and between interfaces of theLDD 43 and the first, second and third spacers 42, 47, 51.

Referring to FIG. 14C, the embedded stressor 65 may be formed to have adesired horizontal width by adjusting the thickness of the second spacer47A. For example, the embedded stressor 65 may be formed at an outerside of the first gate electrode 77.

Referring to FIG. 14D, the bottom of the embedded stressor 65 may belocated in the halo 45.

Referring to FIG. 14E, an embedded stressor 65A may include a firstsemiconductor layer 61A, the second semiconductor layer 62, and thethird semiconductor layer 63. The first semiconductor layer 61A may beformed to cover the second side surface 23S2 with a constant thicknessand to partially expose the first side surface 2351. The secondsemiconductor layer 62 may be in contact with the first side surface23S1.

Referring to FIG. 14F, an embedded stressor 65B may include a firstsemiconductor layer 61B, the second semiconductor layer 62, and thethird semiconductor layer 63. The first semiconductor layer 61B may beformed to cover the first side surface 23S1 and the second side surface23S2. The first semiconductor layer 61B may be formed between the LDD 43and the second semiconductor layer 62.

Referring to FIG. 14G the faster etch rate part 49 may be retainedbetween the embedded stressor 65 and the LDD 43.

FIG. 15 is a cross-sectional view illustrating an intermediate structureprovided in operations of forming a semiconductor device according tosome embodiments of the present inventive concepts. Referring to FIG.15, a well 22, an active region 23, a device isolation layer 29, a gatedielectric layer 131, a first gate electrode 133, a second gateelectrode 181, an inner spacer 134, a first spacer 142, a lightly dopeddrain (LDD) 43, a halo 45, a second spacer 147, a third spacer 151, anembedded stressor 65, an etch stopping layer 183, and an interlayerinsulating layer 185 may be formed on the substrate 21. The gatedielectric layer 131 and the first gate electrode 133 may be formedbefore forming the embedded stressor 65.

The gate dielectric layer 131 may include silicon oxide, siliconnitride, silicon oxy-nitride, a high-K dielectric layer, or acombination thereof. The first gate electrode 133 may include aconductive layer such as polysilicon, a metal silicide, a metal, or acombination thereof. The second gate electrode 181 may include aconductive layer such as a metal silicide, a metal, or a combinationthereof. The inner spacer 134 may include silicon oxide, siliconnitride, silicon oxy-nitride, or a combination thereof. The etchstopping layer 183 may include a material having an etch selectivitywith respect to the interlayer insulating layer 185. For example, theinterlayer insulating layer 185 may include silicon oxide, and the etchstopping layer 183 may include silicon nitride.

FIG. 16 is a layout of a semiconductor device according to someembodiments of the present inventive concepts. FIGS. 17-24, 25A-25C,26-30, and 31A-31C are cross-sectional views taken along lines I-I′ andII-II′ of FIG. 16 illustrating intermediate structures provided inoperations of forming a semiconductor device according to someembodiments of the present inventive concepts.

Referring to FIGS. 16 and 17, a device isolation layer 229 defining anactive region 223 may be formed on a substrate 221. An upper surface ofthe active region 223 may be covered by a buffer layer 225. The activeregion 223 may have various shapes such as a fin-shape or wire-shape.For example, the active region 223 may include a fin-shaped singlecrystalline silicon in which the major axis is formed to be relativelylong.

Referring to FIGS. 16 and 18, a well 222 may be formed in apredetermined region of the substrate 221. The active region 223 may beconfined to the well 222. Channel ions may be implanted in the activeregion 223. The well 222 may be formed by implanting impurities having aconductivity type different from that of impurities in the substrate221. For example, the well 222 may be formed by implanting n-typeimpurities to a predetermined depth from the surface of the substrate221. In some embodiments, the well 222 may be formed before theformation of the device isolation layer 229. In some embodiments, thewell 222 may be omitted.

Referring to FIGS. 16 and 19, side surfaces of the active region 223 maybe exposed by recessing the device isolation layer 229. The deviceisolation layer 229 may be retained at a lower level than an upper endof the active region 223. While recessing the device isolation layer229, the buffer layer 225 may also be removed. The upper surface of theactive region 223 may be exposed. An etch-back process may be performedin the recess of the device isolation layer 229.

Referring to FIGS. 16 and 20, a temporary gate dielectric layer 231, atemporary gate electrode 233, a first mask pattern 235, and a secondmask pattern 237 may be formed on the active region 223. The temporarygate electrode 233 may be formed by a thin film formation process, a CMPprocess, and a patterning process.

The temporary gate electrode 233 may cross the active region 223. Thetemporary gate electrode 233 may cover side and upper surfaces of theactive region 223. The temporary gate dielectric layer 231 may be formedbetween the active region 223 and the temporary gate electrode 233. Thetemporary gate dielectric layer 231 may include an insulating materialsuch as silicon oxide, silicon nitride, silicon oxy-nitride, or acombination thereof. The temporary gate electrode 233 may includepolysilicon. The first mask pattern 235 may include silicon oxide. Thesecond mask pattern 237 may include silicon nitride.

Referring to FIGS. 16 and 21, a first spacer 242 may be formed on sidesurfaces of the temporary gate electrode 233. A lightly doped drain(LDD) 243 and a halo 245 may be formed in the active region 223. Thefirst spacer 242 may cover side surfaces of the temporary gate electrode233, the first mask pattern 235, and the second mask pattern 237. Thefirst spacer 242 may include an insulating layer such as silicon oxide,silicon nitride, silicon oxy-nitride, or a combination thereof. Forexample, the first spacer 242 may be silicon nitride.

The LDD 243 and the halo 245 may be formed using the second mask pattern237 and the first spacer 242 as an ion-implantation mask. The LDD 243may be formed in the active region 223 adjacent to an outer side of thetemporary gate electrode 233. The LDD 243 may diffuse under the firstspacer 242. The LDD 243 may include impurities having a conductivitytype different from that of impurities in the well 222. For example, theLDD 243 may include p-type impurities. The LDD 243 may include boron.

The halo 245 may be formed outside of the LDD 243. The halo 245 maycover a bottom and side surfaces of the LDD 243. The halo 245 mayinclude impurities having a conductivity type different from that ofimpurities in the LDD 243, and the halo 245 may include impuritieshaving a conductivity type that is same as that of impurities in thewell 222. For example, the halo 245 may include n-type impurities. Theconcentration of the n-type impurities of the halo 245 may be higherthan that of the well 222.

Referring to FIGS. 16 and 22, a second spacer 247 may be formed on thefirst spacer 242. A faster etch rate part 249 may be formed in theactive region 223 using the second spacer 247 as an ion-implantationmask. The faster etch rate part 249 may include phosphorous. The secondspacer 247 may conformally cover the substrate 221. The second spacer247 may include a material having an etch selectivity with respect tothe temporary gate electrode 233. For example, the second spacer 247 mayinclude silicon nitride.

The faster etch rate part 249 may be formed at a desired position byadjusting the thickness of the second spacer 247. The faster etch ratepart 249 may be formed in the LDD 243. A bottom of the faster etch ratepart 249 may be formed at a higher level than that of the LDD 243. Thefaster etch rate part 249 may be formed to be aligned with an outer sideof the temporary gate electrode 233. The active region 223 may beretained under the temporary gate electrode 233. The LDD 243 may beretained under the temporary gate electrode 233. The LDD 243 may beretained between the faster etch rate part 249 and the active region223.

Referring to FIGS. 16 and 23, a third spacer 251 may be formed on thesecond spacer 247. The formation of the third spacer 251 may include athin-film formation process and an anisotropic etching process. Whileforming the third spacer 251, the second spacer 247 and the first spacer242 may be partially removed to expose an upper surface of the fasteretch rate part 249. The second spacer 247 and the first spacer 242 maybe retained between the temporary gate electrode 233 and the thirdspacer 251.

Referring to FIGS. 16 and 24, a first trench 253 may be formed byetching the faster etch rate part 249 and the LDD 243. The first trench253 may include an upper trench 253A aligned with the faster etch ratepart 249 and a lower trench 253B connected to a bottom of the uppertrench 253A. The upper trench 253A may be formed in the LDD 243. Anunder-cut may be formed under the first spacer 242, the second spacer247, and the third spacer 251 by the upper trench 253A. A sidewall ofthe first trench 253 may have a step. For example, the side surface ofthe LDD 243, which is exposed by the upper trench 253A and lower trench253B, may have the step.

The formation of the first trench 253 may include a dry-etch process, awet-etch process, or a combination thereof. The formation of the firsttrench 253 may include an isotropic etching process, an anisotropicetching process, or a combination thereof. For example, the formation ofthe first trench 253 may include an isotropic dry-etch process usingHBr, CF₄, O₂, Cl₂, NF₃, or a combination thereof. According to someembodiments, single crystalline silicon including phosphorous, which hasan etch rate higher than that of single crystalline silicon includingboron, may be included in the faster etch rate part 249, and thus thefaster etch rate part 249 may have an etch rate higher than that of theLDD 243. Sizes and shapes of the upper trench 253A and lower trench 253Bmay be determined depending on the configuration of the faster etch ratepart 249 and the LDD 243.

Referring to FIGS. 16 and 25A, a second trench 255 may be formed using adirectional etch process. For example, the formation of the secondtrench 255 may include a wet-etch process using NH₄OH, NH₃OH, TMAH(Tetra Methyl Ammonium Hydroxide), KOH, NaOH, BTMH(benzyltrimethylammonium hydroxide), or a combination thereof. Thedirectional etch process may have different etch rates depending oncrystal orientations of the active region 223. The second trench 255 maypass through the LDD 243. The LDD 243 may be retained between the secondtrench 255 and the active region 223.

The active region 223 may include a first surface 223SU, a first sidesurface 223S1, a second side surface 223S2, a third side surface 223S3,and a second surface 223S4. Each of the first side surface 223S1, thesecond side surface 223S2, and the third side surface 223S3 may includea {111} crystal plane. The first surface 223SU may be formed on theupper end of the active region 223. The first side surface 223S1 may beconnected to the first surface 223SU. The first side surface 223S1 mayform an acute angle with respect to the first surface 223SU. The secondside surface 223S2 may be formed under the first side surface 223S1. Thesecond side surface 223S2 may have a slope different from that of thefirst side surface 223S1. The second side surface 223S2 may beperpendicular to the substrate 221. The third side surface 223S3 may beformed under the second side surface 223S2. The third side surface 223S3may have a slope different from that of the second side surface 223S2. Abottom of the second trench 255 may expose the second surface 223S4. Thesecond surface 223S4 may be connected to the third side surface 223S3.

Referring to FIG. 25B, a second trench 255A may be formed in variousshapes depending on crystal orientations of the active region 223. Forexample, the second trench 255A may be a U-shape. The second trench 255Amay expose a first side surface 223S5 and the second surface 223S4. Thefirst side surface 223S5 may be connected to the first surface 223SU.The first side surface 223S5 may be perpendicular to the first surface223SU. The bottom of the second trench 255A may expose the secondsurface 223S4. The second surface 223S4 may be connected to the firstside surface 223S5.

Referring to FIG. 25C, the second trench 255B may expose the first sidesurface 223S1, the second side surface 223S2, and the second surface223S4. The first side surface 223S1 may be connected to the firstsurface 223SU. The first side surface 223S1 may form an acute angle withrespect to the first surface 223SU. The second side surface 223S2 may beformed under the first side surface 223S1. The bottom of the secondtrench 255B may expose the second surface 223S4. The second surface223S4 may be connected to the second side surface 223S2.

Referring to FIGS. 16 and 26, a second semiconductor layer 262 may beformed in the second trench 255. The second semiconductor layer 262 mayinclude B-doped single crystalline SiGe formed by a SEG method. The Gecontent in the second semiconductor layer 262 may be 25 to 50%. Thesecond semiconductor layer 262 may contain 1E20 to 3E20 atoms/cm3 ofboron (B). The second semiconductor layer 262 may fully fill the secondtrench 255. An upper end of the second semiconductor layer 262 may be ata higher level than the active region 223.

Referring to FIGS. 16 and 27, a third semiconductor layer 263 may beformed on the second semiconductor layer 262. The third semiconductorlayer 263 may include B-doped single crystalline Si formed by a SEGmethod. The third semiconductor layer 263 may contain 1E20 to 3E20atoms/cm3 of boron (B). The second semiconductor layer 262 and the thirdsemiconductor layer 263 may form an embedded stressor 265. In someembodiments, the third semiconductor layer 263 may be omitted.

Referring to FIGS. 16 and 28, an interlayer insulating layer 271 may beformed on the substrate 221.

Referring to FIGS. 16 and 29, the temporary gate electrode 233 may beexposed by partially removing the interlayer insulating layer 271 andremoving the second mask pattern 237 and the first mask pattern 235.

Referring to FIGS. 16 and 30, the temporary gate electrode 233 and thetemporary gate dielectric layer 231 may be removed to form a gate trench233T exposing the active region 223.

Referring to FIGS. 16 and 31A, a first gate dielectric layer 273, asecond gate dielectric layer 275, and a gate electrode 279 may be formedin the gate trench 233T. The embedded stressor 265 may have awedge-shape.

The first gate dielectric layer 273 may be formed on the active region223. The first gate dielectric layer 273 may be referred to as aninterfacial oxide layer. The first gate dielectric layer 273 may beformed by a cleaning process. The first gate dielectric layer 273 mayinclude silicon oxide. The second gate dielectric layer 275 may includesilicon oxide, silicon nitride, silicon oxy-nitride, a high-K dielectriclayer, or a combination thereof. The second gate dielectric layer 275may surround a side and a bottom of the gate electrode 279. The firstgate dielectric layer 273 may be interposed between the active region223 and the second gate dielectric layer 275.

Referring to FIG. 31B, the embedded stressor 265 may include a secondsemiconductor layer 262A and a third semiconductor layer 263. Theembedded stressor 265 may be a U-shape.

Referring to FIG. 31C, the embedded stressor 265 may include a secondsemiconductor layer 262B and a third semiconductor layer 263. Theembedded stressor 265 may be a pyramid-shape or a pencil-shape.

FIG. 32 is a layout of a semiconductor device according to someembodiments of the present inventive concepts. FIGS. 33-38 arecross-sectional views illustrating intermediate structures provided inoperations of forming a semiconductor device according to someembodiments of the present inventive concepts.

Referring to FIG. 32, a semiconductor chip 100 may include a firstregion 102 and a second region 101C. The first region 102 may bereferred to as a logic region. The second region 101C may be referred toas a cell array region. A plurality of PMOS transistors may be formed inthe first region 102 and the second region 101C. The second region 101Cmay have a pattern density higher than that of the first region 102.

The semiconductor chip 100 may be a microprocessor. The semiconductorchip 100 may include a memory region 101. The memory region 101 mayinclude the second region 101C and an SRAM-peripheral region 101P. Thesecond region 101C may include memory cells such as an SRAM. The firstregion 102 may be formed adjacent to the memory region 101.

Referring to FIGS. 32 and 33, a first well 22, a first active region 23,a first device isolation layer 29, a first buffer layer 31, a firsttemporary gate electrode 33, a first lower mask pattern 35, and a firstupper mask pattern 37 may be formed in the first region 102 of asubstrate 21. The substrate 21 may include first conductivity-typeimpurities. The first well 22 may include second conductivity-typeimpurities different from the first conductivity-type impurities.Hereinafter, the description will be made under the assumption that thefirst conductivity is p-type and the second conductivity is n-type.

The first active region 23 may be confined to the first well 22 by thefirst device isolation layer 29. The first temporary gate electrode 33may be formed to cross the first active region 23. The first upper maskpattern 37, the first lower mask pattern 35, the first temporary gateelectrode 33, and the first buffer layer 31 may be referred to as afirst temporary gate pattern 31, 33, 35, and 37. The first temporarygate pattern 31, 33, 35, and 37 may cross the first active region 23. Aplurality of the first temporary gate patterns 31, 33, 35, and 37 may beformed in parallel on the first active region 23.

A first inner spacer 42 may be formed on a sidewall of the firsttemporary gate electrode 33. A first LDD 43 may be formed by implantingthe first conductivity-type impurities in the first active region 23using the first inner spacer 42, the first upper mask pattern 37, thefirst lower mask pattern 35, and the first temporary gate electrode 33as an ion-implantation mask. A first halo 45 may be formed by implantingthe second conductivity-type impurities in the first active region 23.The first halo 45 may cover a side and a bottom of the first LDD 43. Theformation of the first LDD 43 and the first halo 45 may include anion-implantation process and a heat treatment process.

A first intermediate spacer 47 may be formed on the first inner spacer42. A first faster etch rate part 49 may be formed in the first activeregion 23 using the first intermediate spacer 47 as an ion-implantationmask. A first outer spacer 51 may be formed on the first intermediatespacer 47. The formation of the first outer spacer 51 may include a thinfilm formation process and an anisotropic etching process. An uppersurface of the first faster etch rate part 49 may be exposed.

A second well 322, a second active region 323, a second device isolationlayer 329, a second buffer layer 331, a second temporary gate electrode333, a second lower mask pattern 335, and a second upper mask pattern337 may be formed in the second region 101C of the substrate 21. Thesecond well 322 may include second conductivity-type impurities.

The second active region 323 may be confined to the second well 322 bythe second device isolation layer 329. The second temporary gateelectrode 333 may be formed to cross the second active region 323. Thesecond upper mask pattern 337, the second lower mask pattern 335, thesecond temporary gate electrode 333, and the second buffer layer 331 maybe referred to as a second temporary gate pattern 331, 333, 335, and337. The second temporary gate pattern 331, 333, 335, and 337 may crossthe second active region 323. A plurality of the second temporary gatepatterns 331, 333, 335, and 337 may be formed in parallel on the secondactive region 323.

A second inner spacer 342 may be formed on a sidewall of the secondtemporary gate electrode 333. A second LDD 343 may be formed byimplanting the first conductivity-type impurities in the second activeregion 323 using the second inner spacer 342, the second upper maskpattern 337, the second lower mask pattern 335, and the second temporarygate electrode 333 as an ion-implantation mask. A second halo 345 may beformed by implanting the second conductivity-type impurities in thesecond active region 323. The second halo 345 may cover a side and abottom of the second LDD 343. The formation of the second LDD 343 andthe second halo 345 may include an ion-implantation process and a heattreatment process.

A second intermediate spacer 347 may be formed on the second innerspacer 342. A second faster etch rate part 349 may be formed in thesecond active region 323 using the second intermediate spacer 347 as anion-implantation mask. A second outer spacer 351 may be formed on thesecond intermediate spacer 347. The formation of the second outer spacer351 may include a thin film formation process and an anisotropic etchingprocess. An upper surface of the second faster etch rate part 349 may beexposed.

The first LDD 43 and the second LDD 343 may contain boron. The secondLDD 343 may have a boron concentration higher than that of the first LDD43. The first faster etch rate part 49 and the second faster etch ratepart 349 may contain phosphorous. The second faster etch rate part 349may have a phosphorous concentration lower than that of the first fasteretch rate part 49.

In some embodiments, the second LDD 343 may contain a boronconcentration higher than that of the first LDD 43, and the secondfaster etch rate part 349 may contain a phosphorous concentration lowerthan that of the first faster etch rate part 49. In some embodiments,the second faster etch rate part 349 may be omitted.

Referring to FIGS. 32 and 34, the first faster etch rate part 49, thefirst LDD 43, and the first halo 45 may be etched to form a firstpreliminary trench 53. The first preliminary trench 53 may include afirst upper trench 53A aligned with the first faster etch rate part 49and a first lower trench 53B connected to a bottom of the first uppertrench 53A. The first upper trench 53A may be formed in the first LDD43. The first lower trench 53B may pass through the first LDD 43 to beformed in the first halo 45. The first lower trench 53B may have a widthsmaller than a width of the first upper trench 53A. A sidewall of thefirst preliminary trench 53 may have a step. For example, a sidewall ofthe first LDD 43, which is exposed by the first upper trench 53A and thefirst lower trench 53B, may have a step.

The second faster etch rate part 349, the second LDD 343, and the secondhalo 345 may be etched to form a second preliminary trench 353. Thesecond preliminary trench 353 may include a second upper trench 353Aaligned with the second faster etch rate part 349 and a second lowertrench 353B connected to a bottom of the second upper trench 353A. Thesecond upper trench 353A may be formed in the second LDD 343. The secondlower trench 353B may pass through the second LDD 343 to be formed inthe second halo 345. The second lower trench 353B may have a widthsmaller than that of the second upper trench 353A. A sidewall of thesecond preliminary trench 353 may have a step. For example, a sidewallof the second LDD 343, which is exposed by the second upper trench 353Aand the second lower trench 353B, may have a step.

The formation of the first preliminary trench 53 and the secondpreliminary trench 353 may include a dry-etch process, a wet-etchprocess, or a combination thereof. The formation of the firstpreliminary trench 53 and the second preliminary trench 353 may includean isotropic etching process, an anisotropic etching process, or acombination thereof. For example, the formation of the first preliminarytrench 53 and the second preliminary trench 353 may include an isotropicdry-etch process using HBr, CF₄, O₂, Cl₂, NF₃, or a combination thereof.According to some embodiments, the second LDD 343 having a boronconcentration higher than that of the first LDD 43 may have an etch ratelower than that of the first LDD 43. According to some embodiments, thesecond faster etch rate part 349 having a phosphorous concentrationlower than that of the first faster etch rate part 49 may have a loweretch rate than the first faster etch rate part 49.

Depending on the configuration of the first faster etch rate part 49,the second faster etch rate part 349, the first LDD 43, and the secondLDD 343, sizes and shapes of the first upper trench 53A, the first lowertrench 53B, the second upper trench 353A, and the second lower trench353B may be determined. Using the configuration of the first faster etchrate part 49, the second faster etch rate part 349, the first LDD 43,and the second LDD 343, the sizes, the shapes, and the positions of thefirst preliminary trench 53 and the second preliminary trench 353 may becontrolled as desired.

Referring to FIGS. 32 and 35, a first trench 55 in the first activeregion 23 and a second trench 355 in the second active region 323 may beformed using a directional etch process. For example, the formation ofthe first trench 55 and the second trench 355 may include a wet-etchprocess using NH4OH, NH3OH, TMAH (Tetra Methyl Ammonium Hydroxide), KOH,NaOH, BTMH (benzyltrimethylammonium hydroxide), or a combinationthereof.

The first active region 23 may have a first sigma-shape (Σ-shape) due tothe first trench 55. The first LDD 43 may be retained under the firsttemporary gate pattern 31, 33, 35, and 37. The first active region 23may include a first surface 23SU, a first side surface 23S1, a secondside surface 23S2, and a second surface 23S3. A first edge E1 may bedefined between the first side surface 2351 and the first surface 23SU.A second edge E2 may be defined between the first side surface 23S1 andthe second side surface 23S2.

The second active region 323 may have a second sigma-shape (Σ-shape) dueto the second trench 355. The second LDD 343 may be retained under thesecond temporary gate pattern 331, 333, 335, and 337. The second activeregion 323 may include a third surface 323SU, a third side surface323S1, a fourth side surface 323S2, and a fourth surface 323S3. A thirdedge E31 may be defined between the third side surface 323S1 and thethird surface 323SU. A fourth edge E32 may be defined between the thirdside surface 323S1 and the fourth side surface 323S2.

The first trench 55 may be interpreted as an extension of the firstpreliminary trench 53, and the second trench 355 may be interpreted asan extension of the second preliminary trench 353.

Referring to FIGS. 32 and 36, the first trench 55 may pass through thefirst LDD 43 and the first halo 45. The first surface 23SU may bedefined on an upper end of the first active region 23. For example, thefirst surface 23SU may be in contact with the first buffer layer 31 andextend under the first inner spacer 42. The first trench 55 may exposethe first side surface 23S1, the second side surface 23S2, and thesecond surface 23S3. The first side surface 23S1 may be connected to thefirst surface 23SU. The first side surface 23S1 may form an acute anglewith respect to the first surface 23SU. The second side surface 23S2 maybe formed under the first side surface 23S1. The second side surface23S2 may have a slope different from that of the first side surface23S1. The second side surface 23S2 may form an acute angle with respectto a horizontal extension line which is parallel to the substrate 21 andpass through the second surface 23S3. A bottom of the first trench 55may expose the second surface 23S3. The second surface 23S3 may beconnected to the second side surface 23S2. The first surface 23SU may beinterpreted as an upper surface of the first active region 23.

The second trench 355 may pass through the second LDD 343 and the secondhalo 345. The third surface 323SU may be defined on an upper end of thesecond active region 323. For example, the third surface 323SU may be incontact with the second buffer layer 331 and extend under the secondinner spacer 342. The second trench 355 may expose the third sidesurface 323S1, the fourth side surface 323S2, and the fourth surface323S3. The third side surface 323S1 may be connected to the thirdsurface 323SU. The third side surface 32351 may form an acute angle withrespect to the third surface 323SU. The fourth side surface 323S2 may beformed under the third side surface 323S1. The fourth side surface 323S2may have a slope different from that of the third side surface 323S1.The fourth side surface 323S2 may form an acute angle with respect to ahorizontal extension line which is parallel to the substrate 21 and passfourth surface 323S3. A bottom of the second trench 355 may expose thefourth surface 323S3. The fourth surface 323S3 may be connected to thefourth side surface 323S2. The third surface 323SU may be interpreted asan upper surface of the second active region 323.

Using the configuration of the first LDD 43 and the first faster etchrate part 49, the first edge E1 and the second edge E2 may be formed atdesired positions. For example, first edge E1 may be formed under thefirst inner spacer 42, and the second edge E2 may be formed to beoverlapped by the first temporary gate electrode 33. The first edge E1and the second edge E2 may be located at a surface of the first LDD 43.The first side surface 23S1 may expose the first LDD 43. The second sidesurface 23S2 may expose the first LDD 43, the first halo 45, and thefirst active region 23.

Using the configuration of the second LDD 343 and the second faster etchrate part 349, the third edge E31 and the fourth edge E32 may be formedat a desired position. For example, the third edge E31 may be formedunder the second inner spacer 342, and the fourth edge E32 may bealigned with an outer side of the second temporary gate electrode 333.The third edge E31 and the fourth edge E32 may be located on a surfaceof the second LDD 343. The third side surface 323S1 may expose thesecond LDD 343. The fourth side surface 323S2 may expose the second LDD343, the second halo 345, and the second active region 323.

A first horizontal distance X1 may be defined between the second edge E2and a straight line passing through a side surface of the firsttemporary gate electrode 33 and perpendicular to the substrate 21. Afirst vertical height Y1 may be defined between the second edge E2 and astraight line passing through the first surface 23SU and parallel to thesubstrate 21. For example, the first horizontal distance X1 may be zeroto −5 nm, and the first vertical height Y1 may be 3 nm to 7 nm. It maybe interpreted that when the first horizontal distance X1 is zero, thesecond edge E2 is vertically overlapped by the side surface of the firsttemporary gate electrode 33, and when the first horizontal distance X1is a negative value, the second edge E2 is vertically overlapped by abottom of the first temporary gate electrode 33.

A second horizontal distance X3 may be defined between the fourth edgeE32 and a straight line passing through a side surface of the secondtemporary gate electrode 333 and perpendicular to the substrate 21. Asecond vertical height Y3 may be defined between the fourth edge E32 anda straight line passing through the third surface 323SU and parallel tothe substrate 21. The fourth edge E32 may be formed at a lower levelthan the second edge E2. For example, the second horizontal distance X3may be from +1 nm to +3 nm, and the second vertical height Y3 may befrom 8 nm to 12 nm. It may be interpreted that when the secondhorizontal distance X3 is a positive value, the second temporary gateelectrode 333 does not overlap the fourth edge E32.

Referring to FIGS. 32 and 37, a first semiconductor layer 61 may beformed in the first trench 55. A second semiconductor layer 62 may beformed on the first semiconductor layer 61. A third semiconductor layer63 may be formed on the second semiconductor layer 62. The firstsemiconductor layer 61, the second semiconductor layer 62, and the thirdsemiconductor layer 63 may form a first embedded stressor 65.

A fourth semiconductor layer 361 may be formed in the second trench 355.A fifth semiconductor layer 362 may be formed on the fourthsemiconductor layer 361. A sixth semiconductor layer 363 may be formedon the fifth semiconductor layer 362. The fourth semiconductor layer361, the fifth semiconductor layer 362, and the sixth semiconductorlayer 363 may form a second embedded stressor 365. The fourthsemiconductor layer 361 may include the same material layer formedconcurrently with the first semiconductor layer 61, the fifthsemiconductor layer 362 may include the same material layer formedconcurrently with the second semiconductor layer 62, and the sixthsemiconductor layer 363 may include the same material layer formedconcurrently with the third semiconductor layer 63.

A first interlayer insulating layer 71 and a second interlayerinsulating layer 371 may be formed on the substrate 21. The firsttemporary gate pattern 31, 33, 35, and 37 may be removed to expose thefirst active region 23, and the second temporary gate pattern 331, 333,335, and 337 may be removed to expose the second active region 323.

A first gate dielectric layer 73, a second gate dielectric layer 75, afirst gate electrode 77, and a second gate electrode 79 may be formed onthe first active region 23. A third gate dielectric layer 373, a fourthgate dielectric layer 375, a third gate electrode 377, and a fourth gateelectrode 379 may be formed on the second active region 323. The thirdgate dielectric layer 373 may have a similar configuration to the firstgate dielectric layer 73, the fourth gate dielectric layer 375 may havea similar configuration to the second gate dielectric layer 75, thethird gate electrode 377 may have a similar configuration to the firstgate electrode 77, and the fourth gate electrode 379 may have a similarconfiguration to the second gate electrode 79.

Referring to FIGS. 32 and 38, the first embedded stressor 65 may passthrough the first LDD 43 and the first halo 45 to be in contact with thefirst active region 23. A bottom of the first embedded stressor 65 maybe formed at a lower level than the first halo 45. The first embeddedstressor 65 may be in contact with the first side surface 23S1 and thesecond side surface 23S2. The second embedded stressor 365 may passthrough the second LDD 343 and the second halo 345 to be in contact withthe second active region 323. A bottom of the second embedded stressor365 may be formed at a lower level than the second halo 345. The secondembedded stressor 365 may be in contact with the third side surface32351 and the fourth side surface 323S2.

The second edge E2 may be formed on a surface of the first LDD 43, andthe fourth edge E32 may be formed on a surface of the second LDD 343.The second edge E2 may be formed at a higher level than the fourth edgeE32. The second edge E2 may overlap a bottom of the first gate electrode77, and the fourth edge E32 may be aligned with an outer side of thethird gate electrode 377.

FIGS. 39 and 40 are a perspective view and a block diagram of anelectronic apparatus, respectively, according to some embodiments of thepresent inventive concepts. Referring to FIG. 39, the semiconductordevice according to some embodiments may be applied to electronicsystems such as a smart phone 1900, a netbook, a notebook, or a tabletPC. For example, the semiconductor device according to some embodimentsmay be installed in a main board of the smart phone 1900. Further, thesemiconductor device according to some embodiments may be provided to anexpansion apparatus such as an external memory card to be combined withthe smart phone 1900.

Referring to FIG. 40, the semiconductor device according to someembodiments may be applied to an electronic system 2100. The electronicsystem 2100 may include a body 2110, a microprocessor unit 2120, a powerunit 2130, a function unit 2140, and/or a display controller unit 2150.The body 2110 may be a motherboard formed of a printed circuit board(PCB). The microprocessor unit 2120, the power unit 2130, the functionunit 2140, and the display controller unit 2150 may be mounted orinstalled on the body 2110. A display unit 2160 may be arranged insideor outside of the body 2110. For example, the display unit 2160 may bearranged on a surface of the body 2110 and display an image processed bythe display controller unit 2150.

The power unit 2130 may receive a constant voltage from an externalbattery, etc., divide the voltage into various levels, and supply thosevoltages to the microprocessor unit 2120, the function unit 2140, andthe display controller unit 2150, etc. The microprocessor unit 2120 mayreceive a voltage from the power unit 2130 to control the function unit2140 and the display unit 2160. The function unit 2140 may performvarious functions of the electronic system 2100. For example, when theelectronic system 2100 is a mobile phone, the function unit 2140 mayhave several components which can perform mobile phone functions such asoutput of an image to the display unit 2160 or output of a voice to aspeaker, by dialing or communication with an external apparatus 2170. Ifa camera is installed, the function unit 2140 may function as an imageprocessor.

According to some embodiments, when the electronic system 2100 isconnected to a memory card, etc. in order to expand capacity, thefunction unit 2140 may be a memory card controller. The function unit2140 may exchange signals with the external apparatus 2170 through awired or wireless communication unit 2180. In addition, when theelectronic system 2100 needs a universal serial bus (USB), etc. in orderto expand functionality, the function unit 2140 may function as aninterface controller. Further, the function unit 2140 may include a massstorage apparatus.

The semiconductor device according to some embodiments may be applied tothe function unit 2140 or the microprocessor unit 2120. For example, themicroprocessor unit 2120 may include the embedded stressor 65. Themicroprocessor unit 2120 may have good electrical characteristics due tothe configuration of the embedded stressor 65.

FIG. 41 is a block diagram of an electronic system according to someembodiments of the present inventive concepts. Referring to FIG. 41, theelectronic system 2400 may include at least one of semiconductor devicesaccording to some embodiments. The electronic system 2400 may be used tofabricate a mobile apparatus or a computer. For example, the electronicsystem 2400 may include a memory system 2412, a microprocessor 2414, arandom access memory (RAM) 2416, a bus 2420, and a user interface 2418.The microprocessor 2414, the memory system 2412, and the user interface2418 may be connected each other via the bus 2420. The user interface2418 may be used to input/output data to/from the electronic system2400. The microprocessor 2414 may program and control the electronicsystem 2400. The RAM 2416 may be used as an operation memory of themicroprocessor 2414. The microprocessor 2414, the RAM 2416, and/or othercomponents may be assembled in a single package. The memory system 2412may store codes for operating the microprocessor 2414, data processed bythe microprocessor 2414, or external input data. The memory system 2412may include a controller and a memory.

The microprocessor 2414, the RAM 2416, or the memory system 2412 mayinclude the semiconductor device according to some embodiments. Forexample, the microprocessor 2414 may include the embedded stressor 65.The microprocessor 2414 may have good electrical characteristics due tothe configuration of the embedded stressor 65.

Semiconductor devices according to some embodiments may include anembedded stressor filling a trench formed in an active region. Theformation of the trench may include forming a faster etch rate part byimplanting phosphorous in an LDD, forming a first trench byisotropically etching the faster etch rate part, and forming a secondtrench using a directional etch process. The embedded stressor may fillthe trench. Semiconductor devices according to some embodiments may havegood electrical characteristics because the control of a size, a shape,and a position of the embedded stressor may be easy/improved, thepattern-loading effect may be reduced/minimized, and variation accordingto the position of the active region between the center area and an edgearea may be reduced.

The above-disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments, which fall withinthe true spirit and scope of the inventive concepts. Thus, to themaximum extent allowed by law, the scope is to be determined by thebroadest permissible interpretation of the following claims and theirequivalents, and shall not be restricted or limited by the foregoingdetailed description.

What is claimed is:
 1. A semiconductor device comprising: a substrate;an active region in the substrate; a gate structure disposed on theactive region, the gate structure including a gate dielectric layer, afirst gate electrode, a second gate electrode and a spacer; a firstsemiconductor layer; a second semiconductor layer on the firstsemiconductor layer; a third semiconductor layer on the secondsemiconductor layer; and an isolation layer, wherein the isolation layercontacts the second semiconductor layer, wherein at least one of thefirst semiconductor layer, the second semiconductor layer and the thirdsemiconductor layer contacts the gate structure, wherein the gatedielectric layer is disposed on the active region, and the gatedielectric layer comprises a bottom portion, a first side portion and asecond side portion, wherein the first gate electrode comprises a bottomportion, a first side portion and a second side portion, the bottomportion of the first gate electrode is disposed on the bottom portion ofthe gate dielectric layer, the first side portion of the first gateelectrode is disposed on the first side portion of the gate dielectriclayer, and the second side portion of the first gate electrode isdisposed on the second side portion of the gate dielectric layer,wherein the second gate electrode fills a trench defined by the bottomportion, the first side portion and the second side portion of the firstgate electrode, and wherein a top surface of the bottom portion of thefirst gate electrode is lower than a top surface of the thirdsemiconductor layer.
 2. The semiconductor device of claim 1, wherein atop surface of the isolation layer is lower than a top surface of thesecond semiconductor layer and the top surface of the thirdsemiconductor layer.
 3. The semiconductor device of claim 1, wherein thesecond semiconductor layer contacts a bottom and a side of the spacer.4. The semiconductor device of claim 1, wherein the first semiconductorlayer contacts a bottom of the spacer.
 5. The semiconductor device ofclaim 1, wherein at least a portion of the first semiconductor layer isdisposed directly below the gate dielectric layer.
 6. The semiconductordevice of claim 1, wherein at least a portion of the first semiconductorlayer is disposed directly below the first gate electrode.
 7. Thesemiconductor device of claim 1, wherein the first semiconductor layercomprises a bottom portion and a sloped side portion.
 8. Thesemiconductor device of claim 1, wherein each of the first and secondsemiconductor layers comprises a silicon germanium layer, wherein agermanium concentration of the second semiconductor layer is greaterthan that of the first semiconductor layer, and wherein the thirdsemiconductor layer comprises a silicon layer.
 9. The semiconductordevice of claim 1, wherein the gate dielectric layer includes a firstgate dielectric layer and a second the gate dielectric layer disposed onthe first gate dielectric layer.
 10. The semiconductor device of claim1, further comprising a doped drain disposed in the active region andbelow the gate structure.
 11. A semiconductor device comprising: asubstrate; a first active region and a second active region in thesubstrate; a first gate structure disposed on the first active region,the first gate structure including a first gate electrode and a firstspacer; a second gate structure disposed on the first active region, thesecond gate structure including a second gate electrode and a secondspacer; a third gate structure disposed on the second active region, thethird gate structure including a third gate electrode and a thirdspacer; a fourth gate structure disposed on the second active region,the fourth gate structure including a fourth gate electrode and a fourthspacer; a first semiconductor layer in the first active region; a secondsemiconductor layer on the first semiconductor layer; a thirdsemiconductor layer on the second semiconductor layer; a fourthsemiconductor layer in the second active region; a fifth semiconductorlayer on the fourth semiconductor layer; and a sixth semiconductor layeron the fifth semiconductor layer, wherein at least one of the firstsemiconductor layer, the second semiconductor layer and the thirdsemiconductor layer contacts the first gate structure and the secondgate structure, wherein at least one of the fourth semiconductor layer,the fifth semiconductor layer and the sixth semiconductor layer contactsthe third gate structure and the fourth gate structure, and wherein awidth of a widest part of the second semiconductor layer is greater thana width of a widest part of the fifth semiconductor layer.
 12. Thesemiconductor device of claim 11, wherein a shortest distance betweenthe first gate structure and the second gate structure is greater than ashortest distance between the third gate structure and the fourth gatestructure.
 13. The semiconductor device of claim 11, further comprising:a first isolation layer in the first active region; a second isolationlayer in the second active region; a seventh semiconductor layer in thefirst active region; an eighth semiconductor layer on the seventhsemiconductor layer; a ninth semiconductor layer on the eighthsemiconductor layer; a tenth semiconductor layer in the second activeregion; an eleventh semiconductor layer on the tenth semiconductorlayer; and a twelfth semiconductor layer on the eleventh semiconductorlayer, wherein at least one of the seventh semiconductor layer, theeighth semiconductor layer and the ninth semiconductor layer contactsthe second gate structure and the first isolation layer, wherein atleast one of the tenth semiconductor layer, the eleventh semiconductorlayer and the twelfth semiconductor layer contacts the third gatestructure and the second isolation layer, and wherein a width of awidest part of the eighth semiconductor layer is greater than a width ofa widest part of the eleventh semiconductor layer.
 14. The semiconductordevice of claim 11, wherein a width of the first gate electrode isgreater than a width of the third gate electrode.
 15. The semiconductordevice of claim 11, wherein at least a portion of the firstsemiconductor layer is disposed directly below the first gate electrode,and wherein no portion of the fourth semiconductor layer is disposeddirectly below the third gate electrode.
 16. The semiconductor device ofclaim 11, wherein the first semiconductor layer comprises a bottomportion, a lower sloped side portion connected to the bottom portion ofthe first semiconductor layer, and an upper sloped side portionconnected to the lower sloped side portion of the first semiconductorlayer, wherein the fourth semiconductor layer comprises a bottomportion, a lower sloped side portion connected to the bottom portion ofthe fourth semiconductor layer, and an upper sloped side portionconnected to the lower sloped side portion of the fourth semiconductorlayer, and wherein an angle between the lower sloped side portion andthe upper sloped side portion of the first semiconductor layer is lessthan an angle between the lower sloped side portion and the upper slopedside portion of the fourth semiconductor layer.
 17. A semiconductordevice comprising: a substrate; an active region in the substrate; agate structure disposed on the active region, the gate structureincluding a gate electrode and a spacer; a first semiconductor layer; asecond semiconductor layer on the first semiconductor layer; a thirdsemiconductor layer on the second semiconductor layer; and an isolationlayer, wherein the isolation layer contacts the second semiconductorlayer, wherein at least one of the first semiconductor layer, the secondsemiconductor layer and the third semiconductor layer contacts the gatestructure, and wherein a top surface of the isolation layer is lowerthan a top surface of the second semiconductor layer and a top surfaceof the third semiconductor layer.
 18. The semiconductor device of claim17, wherein at least a portion of the third semiconductor layer isdisposed on the isolation layer.
 19. The semiconductor device of claim17, further comprising a gate dielectric layer disposed on the activeregion, the gate dielectric layer comprising a bottom portion, a firstside portion and a second side portion, wherein the gate electrodeincludes a first gate electrode and a second gate electrode, wherein thefirst gate electrode comprises a bottom portion, a first side portionand a second side portion, the bottom portion of the first gateelectrode is disposed on the bottom portion of the gate dielectriclayer, the first side portion of the first gate electrode is disposed onthe first side portion of the gate dielectric layer, and the second sideportion of the first gate electrode is disposed on the second sideportion of the gate dielectric layer, wherein the second gate electrodefills a trench defined by the bottom portion, the first side portion andthe second side portion of the first gate electrode, and wherein a topsurface of the bottom portion of the first gate electrode is lower thanthe top surface of the third semiconductor layer.
 20. The semiconductordevice of claim 17, wherein the second semiconductor layers comprises asilicon germanium layer, and wherein the third semiconductor layercomprises a silicon layer.